"""Support for Modbus Register sensors."""
import logging
import struct

from typing import Any, Union
import voluptuous as vol

from homeassistant.components.sensor import PLATFORM_SCHEMA
from homeassistant.const import (
    CONF_NAME,
    CONF_OFFSET,
    CONF_SLAVE,
    CONF_STRUCTURE,
    CONF_UNIT_OF_MEASUREMENT,
)
from homeassistant.helpers import config_validation as cv
from homeassistant.helpers.restore_state import RestoreEntity

from . import CONF_HUB, DEFAULT_HUB, DOMAIN as MODBUS_DOMAIN

_LOGGER = logging.getLogger(__name__)

CONF_COUNT = "count"
CONF_DATA_TYPE = "data_type"
CONF_PRECISION = "precision"
CONF_REGISTER = "register"
CONF_REGISTER_TYPE = "register_type"
CONF_REGISTERS = "registers"
CONF_REVERSE_ORDER = "reverse_order"
CONF_SCALE = "scale"

DATA_TYPE_CUSTOM = "custom"
DATA_TYPE_FLOAT = "float"
DATA_TYPE_INT = "int"
DATA_TYPE_UINT = "uint"

REGISTER_TYPE_HOLDING = "holding"
REGISTER_TYPE_INPUT = "input"


def number(value: Any) -> Union[int, float]:
    """Coerce a value to number without losing precision."""
    if isinstance(value, int):
        return value

    if isinstance(value, str):
        try:
            value = int(value)
            return value
        except (TypeError, ValueError):
            pass

    try:
        value = float(value)
        return value
    except (TypeError, ValueError):
        raise vol.Invalid("invalid number {}".format(value))


PLATFORM_SCHEMA = PLATFORM_SCHEMA.extend(
    {
        vol.Required(CONF_REGISTERS): [
            {
                vol.Required(CONF_NAME): cv.string,
                vol.Required(CONF_REGISTER): cv.positive_int,
                vol.Optional(CONF_COUNT, default=1): cv.positive_int,
                vol.Optional(CONF_DATA_TYPE, default=DATA_TYPE_INT): vol.In(
                    [DATA_TYPE_INT, DATA_TYPE_UINT, DATA_TYPE_FLOAT, DATA_TYPE_CUSTOM]
                ),
                vol.Optional(CONF_HUB, default=DEFAULT_HUB): cv.string,
                vol.Optional(CONF_OFFSET, default=0): number,
                vol.Optional(CONF_PRECISION, default=0): cv.positive_int,
                vol.Optional(CONF_REGISTER_TYPE, default=REGISTER_TYPE_HOLDING): vol.In(
                    [REGISTER_TYPE_HOLDING, REGISTER_TYPE_INPUT]
                ),
                vol.Optional(CONF_REVERSE_ORDER, default=False): cv.boolean,
                vol.Optional(CONF_SCALE, default=1): number,
                vol.Optional(CONF_SLAVE): cv.positive_int,
                vol.Optional(CONF_STRUCTURE): cv.string,
                vol.Optional(CONF_UNIT_OF_MEASUREMENT): cv.string,
            }
        ]
    }
)


def setup_platform(hass, config, add_entities, discovery_info=None):
    """Set up the Modbus sensors."""
    sensors = []
    data_types = {DATA_TYPE_INT: {1: "h", 2: "i", 4: "q"}}
    data_types[DATA_TYPE_UINT] = {1: "H", 2: "I", 4: "Q"}
    data_types[DATA_TYPE_FLOAT] = {1: "e", 2: "f", 4: "d"}

    for register in config.get(CONF_REGISTERS):
        structure = ">i"
        if register.get(CONF_DATA_TYPE) != DATA_TYPE_CUSTOM:
            try:
                structure = ">{}".format(
                    data_types[register.get(CONF_DATA_TYPE)][register.get(CONF_COUNT)]
                )
            except KeyError:
                _LOGGER.error(
                    "Unable to detect data type for %s sensor, " "try a custom type",
                    register.get(CONF_NAME),
                )
                continue
        else:
            structure = register.get(CONF_STRUCTURE)

        try:
            size = struct.calcsize(structure)
        except struct.error as err:
            _LOGGER.error(
                "Error in sensor %s structure: %s", register.get(CONF_NAME), err
            )
            continue

        if register.get(CONF_COUNT) * 2 != size:
            _LOGGER.error(
                "Structure size (%d bytes) mismatch registers count " "(%d words)",
                size,
                register.get(CONF_COUNT),
            )
            continue

        hub_name = register.get(CONF_HUB)
        hub = hass.data[MODBUS_DOMAIN][hub_name]
        sensors.append(
            ModbusRegisterSensor(
                hub,
                register.get(CONF_NAME),
                register.get(CONF_SLAVE),
                register.get(CONF_REGISTER),
                register.get(CONF_REGISTER_TYPE),
                register.get(CONF_UNIT_OF_MEASUREMENT),
                register.get(CONF_COUNT),
                register.get(CONF_REVERSE_ORDER),
                register.get(CONF_SCALE),
                register.get(CONF_OFFSET),
                structure,
                register.get(CONF_PRECISION),
            )
        )

    if not sensors:
        return False
    add_entities(sensors)


class ModbusRegisterSensor(RestoreEntity):
    """Modbus register sensor."""

    def __init__(
        self,
        hub,
        name,
        slave,
        register,
        register_type,
        unit_of_measurement,
        count,
        reverse_order,
        scale,
        offset,
        structure,
        precision,
    ):
        """Initialize the modbus register sensor."""
        self._hub = hub
        self._name = name
        self._slave = int(slave) if slave else None
        self._register = int(register)
        self._register_type = register_type
        self._unit_of_measurement = unit_of_measurement
        self._count = int(count)
        self._reverse_order = reverse_order
        self._scale = scale
        self._offset = offset
        self._precision = precision
        self._structure = structure
        self._value = None

    async def async_added_to_hass(self):
        """Handle entity which will be added."""
        state = await self.async_get_last_state()
        if not state:
            return
        self._value = state.state

    @property
    def state(self):
        """Return the state of the sensor."""
        return self._value

    @property
    def name(self):
        """Return the name of the sensor."""
        return self._name

    @property
    def unit_of_measurement(self):
        """Return the unit of measurement."""
        return self._unit_of_measurement

    def update(self):
        """Update the state of the sensor."""
        if self._register_type == REGISTER_TYPE_INPUT:
            result = self._hub.read_input_registers(
                self._slave, self._register, self._count
            )
        else:
            result = self._hub.read_holding_registers(
                self._slave, self._register, self._count
            )
        val = 0

        try:
            registers = result.registers
            if self._reverse_order:
                registers.reverse()
        except AttributeError:
            _LOGGER.error(
                "No response from hub %s, slave %s, register %s",
                self._hub.name,
                self._slave,
                self._register,
            )
            return
        byte_string = b"".join([x.to_bytes(2, byteorder="big") for x in registers])
        val = struct.unpack(self._structure, byte_string)[0]
        val = self._scale * val + self._offset
        if isinstance(val, int):
            self._value = str(val)
            if self._precision > 0:
                self._value += "." + "0" * self._precision
        else:
            self._value = f"{val:.{self._precision}f}"
